Downhole device for gas well deliquification

ABSTRACT

A downhole device comprising: a body section, wherein the body section defines a cavity and has an inner diameter and an outer diameter and a nozzle section at a first end of the body section, wherein the nozzle section defines a cavity and has an inner diameter and an outer diameter.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 61/917,506, filed on Dec. 18, 2013, which is incorporated herein by reference.

BACKGROUND

The present disclosure relates generally to downhole devices useful for gas well deliquification. More specifically, in certain embodiments the present disclosure relates to downhole inserts capable of improving gas lift efficiency and postponing liquid loading and associated methods and systems.

In some gas production wells, a minimum velocity of the gas is desired as it flows up through the production tubing. As long as this minimum velocity is achieved, any produced liquids present in the production stream may be lifted through the production tubing to the surface. The minimum velocity necessary to displace these liquids is often referred to as the “critical velocity.”

As fluids are extracted during production, a gradual loss of the reservoir pressure occurs in some natural gas wells. This loss of reservoir pressure may result in a decreased production flow rate and a decreased production velocity. At some point the velocity of the well fluid may drop below the critical velocity. As a result, any liquids present in the production stream may begin to form droplets and fall down into the well bore or accumulate as a film on the sides of the well bore. As the production velocity further decreases, more and more liquids may accumulate close to the bottom of the well bore. This accumulation may create back pressure on the formation, resulting in a further decrease production flow rate and production velocity. In turn, the reduced production velocity may result in an even greater accumulation of liquids.

A number of technologies for dealing with liquid accumulation are used in the art. One such technology is a velocity string. Briefly, a velocity string is a small-diameter tubing string run inside the production tubing of the well. Preferably the velocity string is configured to produce flow velocities higher than the critical velocity while minimizing flow restrictions beyond that which is necessary to achieve critical velocity. However, the use of a velocity string has several disadvantages. First, a velocity string may unduly restrict the pressure in the well bore resulting in a greatly reduced production rate. Second, velocity strings are typically very difficult to install.

It is desirable to develop a method and system for minimizing the accumulation of liquid in well bores that is easy to install at any time during production and does not result in a reduced production rate.

SUMMARY

The present disclosure relates generally to downhole devices useful for gas well deliquification. More specifically, in certain embodiments the present disclosure relates to downhole inserts capable of improving gas lift efficiency and postponing liquid loading and associated methods and systems.

In one embodiment, the present disclosure provides a downhole device comprising: a body section, wherein the body section defines a cavity and has an inner diameter and an outer diameter and a nozzle section at a first end of the body section, wherein the nozzle section defines a cavity and has an inner diameter and an outer diameter.

In another embodiment, the present disclosure provides well bore system comprising: a well bore; a casing string disposed in the well bore; and a downhole device disposed within the casing string, wherein the downhole device comprises: a body section and a nozzle section at a first end of the body section.

In another embodiment, the present disclosure provides a method comprising: providing a well bore comprising a casing string disposed within the well bore; installing a downhole device within the casing string, wherein the downhole device comprises a body section and a nozzle section at a first end of the body section; and producing gas from the well bore.

The features and advantages of the present disclosure will be readily apparent to those skilled in the art. While numerous changes may be made by those skilled in the art, such changes are within the spirit of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the above recited features and advantages of the disclosure may be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to the embodiments thereof that are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this disclosure and are, therefore, not to be considered limiting of its scope. The figures are not necessarily to scale, and certain features and certain views of the figures may be shown exaggerated in scale or in schematic in the interest of clarity and conciseness.

FIG. 1 is a partial solid model rendering of a downhole device in accordance with certain embodiments of the present disclosure.

FIG. 2 is a cross-sectional view of a downhole device in accordance with certain embodiments of the present disclosure.

FIG. 3 is a cross-sectional view of a well bore system in accordance with certain embodiments of the present disclosure.

FIG. 4 a cross-sectional view of a well bore system in accordance with certain embodiments of the present disclosure.

FIG. 5 is a chart depicting critical velocity and pressure drops for well bores comprising downhole devices in accordance with certain embodiments of the present disclosure.

DETAILED DESCRIPTION

The present disclosure relates generally to downhole devices useful for gas well deliquification. More specifically, in certain embodiments the present disclosure relates to downhole inserts capable of improving gas lift efficiency and postponing liquid loading and associated methods and systems.

The description that follows includes exemplary apparatuses, methods, techniques, and/or instruction sequences that embody techniques of the inventive subject matter. However, it is understood that the described embodiments may be practiced without these specific details.

There may be several potential advantages of the systems and methods discussed herein. One potential advantage is that the apparatuses discussed herein may improve gas lift efficiency in gas/condensate wells and postpone liquid loading. Another potential advantage is that the apparatuses discussed herein are that are easier to install than conventional devices, can be installed after production has already started, and provide much smaller well bore pressure increases compared with conventional velocity strings.

Referring now to FIG. 1, FIG. 1 illustrates a downhole device in accordance with certain embodiments of the present invention. As can be seen in FIG. 1, downhole device 100 may comprise a body section 110 and a nozzle section 120.

In certain embodiments, body section 110 may be a cylindrically shaped portion comprising a first end 111 and a second end 112. In certain embodiments, body section 110 may be hollow and define a cavity. In certain embodiments, body section 110 may comprise an inner diameter and an outer diameter. In certain embodiments, the inner diameter of body section 110 may be from 0.3 inches to 2 inches. In certain embodiments, the outer diameter of body section 110 may be from 2 inches to 5 inches. In certain embodiments, for example when installed in a tubular with an inner diameter (not illustrated in FIG. 1), the outer diameter of body section 110 may be 2 mm smaller than the inner diameter of the tubular. In certain embodiments, oil and gas may be flown through the cavity defined by body section 110.

In certain embodiments, body section 110 may be constructed out of any conventional downhole casing materials. In certain embodiments, body section 110 may be constructed out of carbon steel or any non-wetting anti-corrosion polymer capable of handling high pressure and high temperature. In certain embodiments, body section 110 may be coated with a non-wetting anti-corrosion polymer capable of handling high pressure and high temperature. In certain embodiments, body section 110 may be from 5 feet to 50 feet long.

In certain embodiments, downhole device 100 may comprise one or more nozzle sections 120. In certain embodiments, the one or more nozzle sections 120 may be located at first end 111 of body section 110 and/or second end 112 of body section 110. In certain embodiments, as shown in FIG. 1, first nozzle section 120 may be located at first end 111 of body section 110 and second nozzle section 120 may be located at second end 112 of body section 110. In other embodiments, not illustrated, downhole device 100 may comprise a single nozzle section 120 located at either first end 111 or the second end 112 of body section 110.

In certain embodiments, nozzle section 120 may be construed out of the same material as body section 110. In certain embodiments, body section 110 and nozzle section 120 may be a single piece. In other embodiments, the one or more nozzle sections 120 may be connected to body section 110 by any conventional means.

In certain embodiments, nozzle section 120 may be a generally cylindrically shaped portion. In certain embodiments, nozzle section 120 may be hollow and define a cavity. In certain embodiments, nozzle section 120 may comprise an inner diameter and an outer diameter. In certain embodiments, the inner diameter of nozzle section 120 may taper from a diameter equal to the inner diameter of body section 110 to a diameter equal to the outer diameter of body section 110. In other embodiments, the inner diameter of nozzle section 120 may taper from a diameter equal to the inner diameter of body section 110 to a diameter less than the outer diameter of body section 110. In other embodiments, the inner diameter of nozzle section 120 may taper from a diameter equal to the inner diameter of body section 110 to a diameter that is 25% to 200% greater than the inner diameter of body section 110. In other embodiments, the inner diameter of nozzle section 120 may taper from a diameter equal to the inner diameter of body section 110 to a diameter that is 50% to 150% greater than the inner diameter of body section 110. In certain embodiments, the inner diameter of nozzle section 120 may have a constant taper. In other embodiments, the inner diameter of nozzle section 120 may have a variable taper. In certain embodiments, nozzle section 110 may be from 1 foot to 5 feet long.

In certain embodiments, downhole device 100 may further comprise a mixer 130. In certain embodiments, mixer 130 may be a static mixer. Examples of suitable static mixers include any commercially available static in-line mixer available from Cole-Panner. In certain embodiments, mixer 130 may be disposed within the cavity defined by body section 110. In certain embodiments, mixer 130 may be welded or attached to the nozzle section 120 and/or body section 110. In certain embodiments, mixer 130 may be capable of breaking liquid fragments falling through downhole device 100. In certain embodiments, downhole device 100 may comprise one or two mixers 130.

In certain embodiments, downhole device 100 may further comprise one or more movable balls 140 disposed on an outside surface of body section 110. In certain embodiments, the one or more movable balls 140 may assist with installation of downhole device 100 in a tubular and may provide a 1 mm gap between the outside surface of body section 110 and the tubular.

Referring now to FIG. 2, FIG. 2 illustrates a cross-sectional view of downhole device 100.

Referring now to FIG. 3, FIG. 3 illustrates well bore system 300 in accordance with certain embodiments of the present disclosure. In certain embodiments, well bore system 300 may comprise a well bore 310 and one or more downhole devices 320.

In certain embodiments, well bore 310 may penetrate an oil and gas well bore. In certain embodiments, well bore 310 may penetrate a gas/condensate well bore. As shown in FIG. 3, in certain embodiments, well bore 310 may be a vertical well bore. In certain embodiments, a portion of well bore 310 may be lined with a casing string 315. In certain embodiments, casing string 315 may be any conventional casing string.

In certain embodiments, the one or more downhole devices 320 may be disposed within well bore 310. In certain embodiments, the one or more downhole devices 320 may comprise any of the features discussed above with respect to downhole device 100. In certain embodiments, the one or more downhole devices 320 may be used to improve gas lift efficiency for volatile oil, to break liquid fragments, and/or to improve liquid dragged efficiency. In certain embodiments, the downhole device may be installed near the bottom of the casing string. In certain embodiments, the downhole device 320 may or may not be installed within 500, 200, 100, 50, 25, 10, or 5 feet from either end of the well bore.

Referring now to FIG. 4, FIG. 4 illustrates well bore system 400 in accordance with certain embodiments of the present disclosure. In certain embodiments, well bore system 400 may comprise a well bore 410 and one or more downhole devices 420.

In certain embodiments, well bore 410 may comprise any of the features discussed above with respect to well bore 310. As shown in FIG. 4, in certain embodiments, well bore 410 may be a horizontal well bore. In certain embodiments, well bore 410 may be lined with a casing string 415. In certain embodiments, casing string 415 may comprise any of the features discussed above with respect to casing string 315.

In certain embodiments, the one or more downhole devices 420 may be disposed within well bore 410. In certain embodiments, the one or more downhole devices 420 may comprise any of the features discussed above with respect to downhole device 100 or downhole device 320. In certain embodiments, the one or more downhole devices 420 may be used to improve gas lift efficiency for volatile oil, to break liquid fragments, and/or to improve liquid dragged efficiency. In certain embodiments, one of the one or more downhole devices 420 may be installed in the horizontal portion of the well bore and one of the one or more downhole devices 420 may be installed in the vertical portion of the well bore. In certain embodiments, when installed in the vertical portion of the well bore, the downhole device 420 may or may not be installed within 500, 200, 100, 50, 25, 10, or 5 feet from the heel of the well bore or either end of the well bore. In certain embodiments, when installed in the horizontal portion of the well bore, the downhole device may or may not be installed within 500, 200, 100, 50, 25, 10, or 5 from the heel of the well bore or the end of the well bore.

It has been discovered that in certain embodiments the downhole devices discussed herein only result in negligible pressure increases when installed within a well bore yet are capable of dramatically decreasing the critical gas rate in the well bore. In certain embodiments, the devices discussed provide for a smaller flow area in their cavities than in the well bore which generates higher gas/liquid velocity. In certain embodiments, this higher gas/liquid velocity improves droplet and gas mixing and lets the mixture reach a higher velocity when it passes through the downhole device. Any fat liquid fragments present in the stream may break at the top of the device near the nozzle sections and the possibility of these fragments falling down through the device is small because of the higher gas/liquid velocity within the device. Any liquid accumulating on the walls of the casing string may be kept in a statistical steady state due to turbulence flow.

In one embodiments, the present disclosure provides a method comprising: providing a well bore comprising a casing string disposed within the well bore; installing a downhole device within the casing string, wherein the downhole device comprises a body section and a nozzle section at a first end of the body section; and producing gas from the well bore

In certain embodiments, the well bore may comprise any type of well bore discussed above with respect to well bore 310 and 410. In certain embodiments, the casing string may comprise any type of casing string discussed above with respect to casing string 315 and casing string 415. In certain embodiments, the downhole device may comprise any type of downhole device discussed above with respect to downhole device 100, 320, and 420.

In certain embodiments, installing the downhole device may comprise installing the downhole device in a casing string before the casing string is placed into the well bore. In other embodiments, installing the downhole device may comprise installing the downhole device in the casing string after the casing string has been placed into the well bore. In certain embodiments, the device may be installed within the casing string before producing gas from the well bore. In certain embodiments, the device may be installed within the casing string after producing gas from the well bore.

In certain embodiments, producing gas from the well bore may comprise allowing gas to pass through the cavity of the downhole device.

In certain embodiments, the method may further comprise using foaming deliquification to improve liquid unloading efficiency. In certain embodiments, a foaming agent may be injected into the well bore near or in the downhole device. In certain embodiments, the foaming agent may disperse any liquid fragments present in the well bore into fine droplets.

To facilitate a better understanding of the present invention, the following examples of certain aspects of some embodiments are given. In no way should the following examples be read to limit, or define, the scope of the invention.

EXAMPLES Example 1

The impact on critical gas rates and total well pressure drops were studied. Critical gas rates and total well pressure drops were measured for a base case, a 3″ case, a 2.5″ case, and a 2.0″ case. For the base case, critical flow rates under normal conditions of a 3.6 inch ID tubing and pressure were measured. For the 3″ case, critical flow rates under normal conditions of a 3.6 inch ID tubing with a downhole device with a 3″ ID were measured. For the 2.5″ case, critical flow rates under normal conditions of a 3.6 inch ID tubing with a downhole device with a 2.5″ ID were measured. For the 2.0″ case, critical flow rates under normal conditions of a 3.6 inch ID tubing with a downhole device with a 2″ ID were measured.

It was surprisingly found that the pressure drop did not vary substantially with the diameter of the downhole device whereas the critical gas rate varied greatly. For the base case, it was observed that the total well pressure drop was 495 psi and that the critical gas rate was 800 q-mscf/day. For the 3″ case, the total well pressure increase slightly to 502 psi but that critical gas rate greatly dropped to 617 q-mscf/day. For the 2.5″ case, the total well pressure again only slightly increase to 519 PSI and the critical gas rate again greatly dropped to 482 q-mscf/day. For the 2.0″ case, the pressure increased to 577 PSI and the critical gas rate greatly reduced to 353 q-mscf/day. FIG. 5 illustrates these results. FIG. 5 shows that while only negligible pressure increases occur due to the new device installation, the critical gas rate decreases dramatically.

Thus it has been shown that the use of the downhole devices discussed herein unexpectedly reduce the critical gas rate relative to the total well pressure drop than would be expected.

While the embodiments are described with reference to various implementations and exploitations, it will be understood that these embodiments are illustrative and that the scope of the inventive subject matter is not limited to them. Many variations, modifications, additions and improvements are possible.

Plural instances may be provided for components, operations or structures described herein as a single instance. In general, structures and functionality presented as separate components in the exemplary configurations may be implemented as a combined structure or component. Similarly, structures and functionality presented as a single component may be implemented as separate components. These and other variations, modifications, additions, and improvements may fall within the scope of the inventive subject matter. 

What is claimed is:
 1. A downhole device comprising: a body section, wherein the body section defines a cavity and has an inner diameter and an outer diameter and a nozzle section at a first end of the body section, wherein the nozzle section defines a cavity and has an inner diameter and an outer diameter.
 2. The downhole device of claim 1, wherein the inner diameter of the body section is from 0.3 inches to 2 inches and the outer diameter of the body section is from 2 inches to 5 inches.
 3. The downhole device of claim 1, wherein the body section has a length of from 5 feet to 50 feet.
 4. The downhole device of claim 1, wherein the inner diameter of the nozzle section tapers from a diameter equal to the inner diameter of the body section to a diameter equal to the outer diameter of the body section.
 5. The downhole device of claim 1, wherein the inner diameter of the nozzle section tapers from a diameter equal to the inner diameter of the body section to a diameter less than the outer diameter of the body section.
 6. The downhole device of claim 1, wherein the inner diameter of the nozzle section tapers from a diameter equal to the inner diameter of the body section to a diameter that is from 25% to 200% greater than the inner diameter of the body section.
 7. The downhole device of claim 1, wherein the nozzle section has a length of from 1 foot to 5 feet.
 8. The downhole device of claim 1, further comprising a second nozzle section at a second end of the body section.
 9. The downhole device of claim 1, further comprising a mixer disposed within the cavity define by the body section.
 10. The downhole device of claim 1, further comprising one or more movable balls disposed on an outside surface of the body section.
 11. A well bore system, comprising: a well bore; a casing string disposed within the well bore; and a downhole device disposed within the casing string, wherein the downhole device comprises: a body section and a nozzle section at a first end of the body section.
 12. The well bores system of claim 11, wherein the downhole device comprises a body section, wherein the body section defines a cavity and has an inner diameter and an outer diameter and a nozzle section at a first end of the body section, wherein the nozzle section defines a cavity and has an inner diameter and an outer diameter.
 13. The well bore system of claim 11, wherein the well bore is a vertical well bore or a horizontal well bore.
 14. The well bore system of claim 11, further comprising a second downhole device disposed within the casing string.
 15. The well bore system of 14, wherein the first downhole device is disposed within the casing string
 16. The well bore system of claim 11, wherein the downhole device is disposed within the casing string near the bottom of the casing string.
 17. A method comprising: providing a well bore comprising a casing string disposed within the well bore; installing a downhole device within the casing string, wherein the downhole device comprises a body section and a nozzle section at a first end of the body section; and producing gas from the well bore.
 18. The method of claim 17, wherein the downhole device comprises a body section, wherein the body section defines a cavity and has an inner diameter and an outer diameter and a nozzle section at a first end of the body section, wherein the nozzle section defines a cavity and has an inner diameter and an outer diameter.
 19. The method of claim 17, wherein the downhole device is installed within the casing string before producing gas from the well bore.
 20. The method of claim 17, wherein the downhole device is installed within the casing string after producing gas from the well bore. 